Electrical utility companies generally provide current fault interrupters on each phase of each power line which, as an example, respond to the grounding of a current-carrying line. For underground power lines, such fault interrupters are located in underground vaults. In order to isolate power line difficulties, the status of potentially involved interrupters must be determined. Fault interrupter status indicators, commonly called faulted current indicators, are used for this purpose; typically, trip flags are used. Other devices supplied by utility companies provide a grounded response which can be observed in the event of power loss by the line being monitored. In order to monitor the faulted current indicators, however, an individual must enter the vault where these devices are located. Generally, interrupter vaults offer poor ambient conditions, with chemical, electrical and fire hazards being the possible cause or result of a fault. Therefore, self-contained breathing apparatus must be available, or the air in the vaults must be replaced using vacuum pumps and pipes. Additionally, the resulting environment must be tested before repair crews are allowed to enter a particular vault with their attendant time delays and cost, rendering the process of identifying the cause of a current fault unacceptable to utility companies.
Trip flag interrupt indicators may be viewed without entering the interrupter vault by mounting the indicators on the cylindrical wall of a manhole providing access to the current fault interrupter vault, as an example. Commercially available indicators are about 2 in. in diameter and about 2½ in. thick. Moreover, the electrical lines being monitored must also be present in the manhole. This amount of clutter makes it difficult for a service person to enter the manhole.
Monitoring the status of current interrupters for high voltage electrical distribution systems may also be achieved by other commercially available devices. Typically, these are powered by internal batteries or wired to an external electric source, both of which require maintenance and, in the case of batteries, replacement of the power source. Moreover, external, hard-wired power sources may be difficult and/or expensive to provide when independent power lines are unavailable, since power for the indicators derived from the wires being monitored becomes unavailable once a fault occurs.
Accordingly, it is an object of the present invention to provide an apparatus for remotely detecting a current interruption in electric utility wires.
Another object of the present invention is to provide an apparatus for detecting current interruption in underground electric utilities such that service personnel can observe the condition of current fault interrupters without entering vaults containing faulted current indicators.
Yet another object of the invention is to provide an apparatus for detecting current interruption without the requirement for battery powered faulted current indicators or indicators powered using the wires to be monitored or wires having the potential for a conductive pathway to ground.
Additional objects, advantages and novel features of the invention will be set forth, in part, in the description that follows, and, in part, will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.